The objective of this proposal is to define the physiological role of the protein kinase Akt and its downstream targets in the etiology of cancer in a highly specific in vivo system. The PI 3-K-Akt signaling axis is critical for tumor progression by impacting cell survival and growth. Little is known, however, concerning the role of Akt in controlling cell motility and invasion, crucial phenotypes which are observed in most aggressive carcinomas, including those of the breast. Recent studies point to distinct functions for Akt1 and Akt2 on the invasive migration of breast cancer cell lines in vitro, where Akt1 functions as an inhibitor of invasive migration, and Akt2 functions as an enhancer. Mechanistic studies have shown that Akt can promote the degradation of the transcription factor NFAT and thus and blunt transcriptional activity. The hypothesis of this proposal is that Akt isoforms have distinct effects on the survival and invasive migration of breast cancer cells and that this is mediated by Akt-mediated regulation and phosphorylation of NFAT, leading to nuclear export and degradation. In Aim 1, we will determine the dose-dependent effects of Akt1 and Akt2 on breast cancer progression in vivo. We will utilize a tissue specific tetracycline regulated siRNA transgene system to modulate expression in a dose dependent manner of the Akt1 and 2 in a tumor metastasis model, specifically in the breast epithelium using the MMTV promoter and DMBA treatment. In Aim 2, we will investigate the mechanism through which Akt isoforms affect breast cancer cell invasive migration through modulation of NFAT activity. We will initially examine NFAT expression in the Akt1 and Akt2 in vivo silencing model. In addition, we propose to generate a transgene with a mutant NFAT which will be sequestered in the nucleus and breed it to both the Akt1 and Akt2 transgenic mouse lines. Tumorigenesis, initiated by DMBA treatment, and subsequent metastasis will be evaluated. The purpose of this work is to understand in detail the genetic pathways that govern breast cancer cell survival and metastasis, which will provide novel avenues for therapeutic intervention.